Re: [Bier] BIERv6 and BIERin6 OAM support discussion

Tianran Zhou <zhoutianran@huawei.com> Thu, 26 November 2020 06:52 UTC

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From: Tianran Zhou <zhoutianran@huawei.com>
To: Gyan Mishra <hayabusagsm@gmail.com>, BIER WG <bier@ietf.org>, Greg Mirsky <gregimirsky@gmail.com>, Greg Shepherd <gjshep@gmail.com>, Michael McBride <michael.mcbride@futurewei.com>, Tony Przygienda <tonysietf@gmail.com>, "Xiejingrong (Jingrong)" <xiejingrong@huawei.com>
Thread-Topic: BIERv6 and BIERin6 OAM support discussion
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Date: Thu, 26 Nov 2020 06:52:48 +0000
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Subject: Re: [Bier] BIERv6 and BIERin6 OAM support discussion
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Hi Greg,

Thanks for your interest on OAM. Let me reply your question here.

@Gyan, thanks for folking this thread.

The way to encapsulate OAM message is very generic, just like MPLS ping and MPLS p2mp ping.
OAM message is in IP+UDP after Bier.
A highlight of this way is it could also apply to draft-ietf-bier-php.

Cheers,
Tianran




From: Gyan Mishra [mailto:hayabusagsm@gmail.com]
Sent: Thursday, November 26, 2020 1:38 PM
To: BIER WG <bier@ietf.org>rg>; Greg Mirsky <gregimirsky@gmail.com>om>; Greg Shepherd <gjshep@gmail.com>om>; Gyan Mishra <hayabusagsm@gmail.com>om>; Michael McBride <michael.mcbride@futurewei.com>om>; Tianran Zhou <zhoutianran@huawei.com>om>; Tony Przygienda <tonysietf@gmail.com>om>; Xiejingrong (Jingrong) <xiejingrong@huawei.com>
Subject: Re: BIERv6 and BIERin6 OAM support discussion

Greg

With RFC 8296 Non MPLS BIER Ethernet next header 0xAB37  and optIonal BIERin6 encapsulation single hop or multi hop tunnel the BIER header is present either after Ethernet header in the latter or after the IPv6 header in BIERin6 and is present to encode OAM value for proto fied.

With BIERv6 there is not any “BIER” encapsulation layer as the BIER header is encoded in IPV6 extension header DOH header.  As it is not encoded in the IPV6 packet header and is part of IPv6 header as is an extension header, OAM will not work natively with BIERv6.


Jingrong and Xuesong

Please shed some light on how OAM would work with BIERv6?

Thanks

Gyan

On Wed, Nov 25, 2020 at 11:47 PM Gyan Mishra <hayabusagsm@gmail.com<mailto:hayabusagsm@gmail.com>> wrote:
RE: BIER in IPV6 environment OAM support

***Tonys email related to OAM requirement***

Quick correction here as to OAM. OAM is worked on and multiple quite extensive & well-written drafts dealing with OAM aspects are adopted/in flight since quite a while (I count 4 adopted & 1 individual). BIER has been specifically architected with multicast OAM in mind which is non-trivial such as MTU discovery (we have 2 drafts for a good reason & discussion is pending) and dealing with OAM when we're dealing with mp2mp trees (which BIER basically is or can be used at). One of the reasons BIER found interest in the set of people that need/like it is that they were looking for very tight OAM guarantees in orders of microseconds and that without highly specific hardware designed for it is very difficult (and packet format, that's why OAM is first order citizen in BIER in terms of bits provided e.g. for marking purposes and can be found in a very specific offset. to support the OAM desired HW has to process and generate sub-microseconds trains.

As far as I saw there was not much on the radar in terms of anything comparable in SRv6 OAM work beside "SID-ping" if the intention is to rely on SRv6 to deal with that problem. But of course I may have missed some draft. Even if they work on unicast OAM I may express my profound doubts there will be interest or focus to solve OAM for SRv6 becoming a L3 multicast transport with the type of OAM BIER needs on top.

As to desired OAM, I think we have an OAM requirements draft adopted with quite a list of industry authors since quite a bit. this draft has WG consensus and has to be satisfied.

https://datatracker.ietf.org/doc/draft-ietf-bier-oam-requirements/?include_text=1

-- tony

Greg Mirsky update request to BIER IPv6 Requirements draft:

Dear All,
I apologize for jumping into this discussion but have someone said "OAM"? :)
I much appreciate what our co-chair (and contributor to BIER OAM) had to say about the state of BIER OAM work. I agree with Tony's summary that our joint efforts already created the toolset of the distinctive solutions for BIER OAM. We've followed draft-ietf-bier-oam-requirements<https://datatracker.ietf.org/doc/draft-ietf-bier-oam-requirements/> to define the comprehensive set of OAM mechanisms that support proactive and on-demand failure detection and localization using both BFD and echo request/reply. Also, as Tony mentioned, we have drafts on path MTU discovery in the BIER environment and application of the Alternate Marking method for the packet delay and packet loss measurement in a BIER domain. In my opinion, the section on OAM in draft-ietf-bier-ipv6-requirements is helpful. I have a question on the intention of the following wording:
.... by specifying a new method for the same functionality.
If there's, for example, WG draft on proactive failure detection in the BIER network using p2mp BFD with unsolicited notifications, why would we entertain the idea of defining a new protocol or method for the same purpose? I think that the ability to use BIER OAM solutions as defined in their respective drafts already accepted by the WG (and some even passed WGLC) is the litmus test for any proposed method of realizing BIER in IPv6 network. Thus I propose the following change of Section 3.1.4<https://tools.ietf.org/html/draft-ietf-bier-ipv6-requirements-09#section-3.1.4>.4>:
OLD TEXT:
   BIER OAM tools like [I-D.ietf-bier-ping] and [I-D.ietf-bier-pmmm-oam]
   should be supported, either directly using existing methods, or by
   specifying a new method for the same functionality.  They are likely
   to be needed in normal BIER deployment for diagnostics.
NEW TEXT:
   BIER OAM tools defined in WG document, for example,
   [I-D.ietf-bier-ping] and [I-D.ietf-bier-pmmm-oam],
   must be supported as defined in the respective specifications. Consistency
   of OAM BIER tools is essential for the productive operation of BIER networks.


Regards,
Greg


RE:  Greg Mirsky start of BIER IPv6 OAM discussion related to the two IPV6 environment solutions

Hi Tianran,
I just recently read both proposals - BIERin6 and BIERv6. Understandably, I was interested in how each solution handles BIER OAM.
draft-zhang-bier-bierin6 explains that:
   BIER has its own OAM function, so generally the IPv6 OAM function is
   not needed.
And I agree with that conclusion. BIER OAM will work because BIER header is used as defined in RFC 8296, including using OAM value in the Proto field.
draft-xie-bier-ipv6-encapsulation states that:
        How BIER-PING is supported in BIERv6
        encapsulation without using this Proto field is outside the
        scope of this document.
That left me with many questions. Thus, from my point of view, BIERv6 needs to demonstrate how BIER OAM, as defined in numerous WG drafts, works in BIERv6 domain. Without that, I cannot compare the two proposals fairly.

Regards,
Greg



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Gyan Mishra

Network Solutions Architect

M 301 502-1347
13101 Columbia Pike
Silver Spring, MD

--

[http://ss7.vzw.com/is/image/VerizonWireless/vz-logo-email]<http://www.verizon.com/>

Gyan Mishra

Network Solutions Architect

M 301 502-1347
13101 Columbia Pike
Silver Spring, MD